Fluorescent penetrant inspection is the most widely used method for the non-destructive inspection of bodies or parts. While various improvements in penetrant formulations have been made over the years, the penetrant inspection process has remained virtually unchanged. In carrying out the process, the part after cleaning is immersed in the penetrant for some period time, e.g., twenty minutes, the part is then cleaned to remove all penetrant except that contained in defects, developer is applied to widen the penetrant indication, and the part is inspected under ultraviolet light.
In some cases removal of excess penetrant is accomplished by water washing. Certain of the more sensitive penetrants must first be emulsified to render them water washable and then water washed. Upon completion of this step, the part is dried, developer is applied, and the inspection is carried out under ultraviolet light. The procedure of applying penetrant, washing, drying, and developing can take as long as an hour and longer.
The above-described conventional non-destructive inspection process has a number of disadvantages which over the years have been of great concern to users. For example, excessive washing can result in removal of penetrant from defects and the application of emulsifier must be carefully controlled. When parts containing penetrant are moved into the emulsifier tank, the emulsifier eventually becomes contaminated with penetrant. As a result the emulsifier must be disposed of and replaced with fresh emulsifier. Inspection must be accomplished within a specific period of time after the developer is applied. If this period is exceeded, the fluorescent indication is lost.
As furnished by a manufacturer, penetrant material usually consists of penetrant, emulsifier and developer. The materials provided by one company are generally not interchangeable with the materials of another company. For example, one company's emulsifier cannot be used with another company's penetrant. This situation results in a supply and logistics problem that has often proven to be troublesome.
It is a principal object of this invention to provide a method for the non-destructive testing of objects that overcomes the various problems associated with the conventional test method.
Another object of the invention is to provide microcapsules containing a fluorescent dye that can be used in a non-destructive inspection method.
Other objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the accompanying disclosure.